An ancestor in the gap
In 2005, a joint Japanese-Kenyan research team found fossils in the Nakali region of central Kenya. Buried in volcanic mudflow deposits, they uncovered a fossil jawbone and eleven isolated teeth. The fossils belonged to a previously unknown species of great ape that lived between 9.9 and 9.8 million years ago, during the late Miocene epoch. This new genus was named Nakalipithecus nakayamai.
The discovery was important because it helped fill a gap in Africa's hominoid fossil record. Before this find, very few ape fossils were known from the continent between 13 and 7 million years ago. This scarcity led some scientists to propose that the common ancestor of African apes and humans might have evolved in Eurasia and later migrated back to Africa. Nakalipithecus shows that great apes continued to evolve in Africa during this period, supporting the continent as the origin point for the human and modern African ape lineages.
Reading the teeth
The primary fossil, a right mandible cataloged as KNM-NA46400, contains three molars. Analysis of the teeth shows the animal's life. The molars are covered in thick enamel and have low, rounded cusps. This dental anatomy suggests a diet that included hard objects like nuts and seeds, supplemented with softer foods like fruit. The size of the jaw and teeth indicates an animal comparable in size to a modern female gorilla or orangutan.
Nakalipithecus shares some characteristics with Ouranopithecus, another fossil ape found in Greece and dated to a slightly younger 9.6 to 8.7 million years ago. However, Nakalipithecus displays more primitive features, such as less rounded cusps on its teeth. This suggests it could be an ancestral species to Ouranopithecus and places it very close to the last common ancestor of gorillas, chimpanzees, and humans, before these lineages diverged. The discovery supports an African origin of the Homininae subfamily.